Device for the dip painting of a body part

ABSTRACT

A device for the dip painting of a body part with a basin for receiving a coating liquid has two parallel guides for guiding the body part and an anode body. The body part is connected to a cathode of a direct voltage source and the anode body to an anode of the direct voltage source. The anode body in position and spacing is assigned to the body part and guided through the basin with the body part. Because of this, adequate coating is ensured also in hollow spaces of the body part.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National-Stage entry under 35 U.S.C. §371based on International Application No. PCT/EP2009/006553, filed Sep. 9,2009, which was published under PCT Article 21(2) and which claimspriority to German Application No. 102008047704.4, filed Sep. 18, 2008,which are all hereby incorporated in their entirety by reference.

TECHNICAL FIELD

The invention relates to a device for the dip painting of a body part ofa motor vehicle with a basin for receiving a coating liquid, with atransport device for the transport of the body part through the basin,with a direct current source, with an anode body connected to the anodeof the direct current source and with a guide connected to the cathodedirect current source for the electrical contacting and moving of thebody part through the basin.

BACKGROUND

Such devices are frequently employed for the dip painting of vehiclebodies such as individual body parts, for example a vehicle door orcomplete body shells and are for example known from DE 196 06 000 C1.With this device, several anode bodies are arranged in the basin and aresupplied with electric current from various direct current sources. Whenguiding the body part through the basin a direct current field developsbetween the anodes and the surface of the body part. The body partattracts dispersion particles from the coating liquid. The coatingliquid, which for example can be a watery dispersion of a baking enamel,is deposited as a layer on the body part.

In addition to the immersion time, the bath temperature and thecomposition of the coating liquid, the layer formation on the body partalso depends on the strength and distribution of the electric directcurrent field. The layer thickness should amount to at least >=20 μm onthe outside and >=10 μm within hollow spaces of the body part. Thearrangement of fixed anodes however results in that on the outside ofthe body part a particularly thick layer and within the hollow spaces aparticularly thin layer is deposited. This results in an undesirablylarge layer thickness on the outside and an undesirably small layerthickness within the hollow spaces of the body part.

To achieve as precise as possible a coating it is known from DE 103 26605 A1 to arrange several anodes distributed over the basin and activatesaid anodes individually with a provided current/voltage characteristiccurve corresponding to the contour of the body part. However, thisresults in a major control effort.

From JP 5 800 3996 (A) a device with a moveable anode body has becomeknown. The anode body is laterally arranged next to the body part. Withthis device, too, only a small layer thickness can be deposited inregions of the body part that are distant from the anode body.

The invention is based on the problem of further developing a device ofthe type mentioned at the outset so that with it the layer thickness canbe established at any point of the body part in as simple as possible amanner.

SUMMARY

According to an embodiment of the invention, this problem is solved inthat the anode body can be mounted in a constant position to the bodypart in movement direction of the body part before and/or behind thebody part and guided through the basin with the body part.

Through this configuration the anode body and the body part can beguided through the bath one after the other. This brings about a highand even field line density and with appropriate selection of thearrangement of the anode body guidable with the body part, a fieldstrength penetration over the entire layer formation process on theregions of the body part, which are not or only inadequately reachedwith anode bodies that are locationally fixed or laterally moved alongnext to the body part. Through the position and alignment of the anodebody with the body part the thickness and the distribution of the directcurrent field between the anode body and the body part can be largelyfreely determined. Since the strength and the distribution of the directcurrent field decisively influence the deposited layer thickness, thelayer thickness thanks to the invention can be easily determined at anypoint of the body part. Thus, an undesirably high deposition on lateralregions of the body part can be avoided and an adequate deposition onhidden regions of the body part ensured at the same time. The deviceavoids a high control effort and can therefore be applied particularlyeasily. Obviously this device can be employed in an anodic method if thepolarity of the direct current source with cathode bodies running alongis reversed.

A preferred deposition of dispersion particles of the coating liquid ina hollow space of the body part can be achieved according to anotheradvantageous further embodiment of the invention if the anode body thatcan be guided through the basin with the body part is arranged in frontof an opening of a hollow space of the body part.

The device according to an embodiment of the invention is of aparticularly simple construction if a further guide connected to theanode of the direct current source is provided and if the anode bodythat can be guided through the basin with the body part is guided on thefurther guide. Preferentially the guides are formed as current rails,from which the body part and the anode body are indirectly suspended.

It contributes to the further simplification of the design structure ofthe device if the two guides are arranged parallel to each other andeach has a holding arm for holding the anode body guidable through thebasin with the body part or of the body part. Through this configurationthe guides can be arranged outside the basin. The holding arms thusconstitute the connections of the guides arranged outside the basin tothe anode bodies and the body part arranged within the basin.

A particularly uniform deposition of dispersion particles of the coatingliquid on the body part can be easily achieved according to anotheradvantageous further embodiment of the invention if the anode bodyguidable through the basin with the body part is designed elongated inshape. The elongated anode body is preferentially arranged parallel tolikewise elongated body parts or in front of an elongated opening in thebody part.

At various points of the body part, layer thicknesses provided accordingto another advantageous further embodiment of the invention can becreated if several anode bodies guidable through the basin with the bodypart are grouped round about the body part. Preferentially an anode bodyguidable through the basin with the body part is mounted on both sidesof the body part.

It is a contribution to the equalization of the deposited layerthicknesses according to another advantageous further embodiment of theinvention if in the basin at least a further fixed anode body connectedto the anode of the direct voltage source is arranged. Through thisconfiguration, both the at least one anode body immovably arranged inthe basin as well as the anode body or bodies guidable through the basinwith the body part each form a direct current field with the body part.Thus, sudden differences of the layer thicknesses deposited on the bodypart are reliably avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and:

FIG. 1 is a schematic of a device according to an embodiment of theinvention with a body part arranged therein; and

FIG. 2 is a sectional representation through a part region of the deviceaccording to the embodiment of the invention from FIG. 1 along the lineII-II.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit application and uses. Furthermore, there is nointention to be bound by any theory presented in the precedingbackground or summary or the following detailed description.

FIG. 1 schematically shows a device for the dip painting of a body part1 formed as vehicle door of a motor vehicle. The device has a basin 2for receiving a coating liquid 3 and the body part 1. In addition,several anode bodies 4 are arranged in the basin 2. The body part 1 isconnected in an electrically conductive manner to a cathode (−) of adirect current source 7. The anode bodies 4-6 are connected to the anode(+) of the direct current source 7.

Two of the anode bodies 4, 5 are arranged in the basin 2 in a fixedmanner, while one of the anode bodies 6 can be moveably guided throughthe basin 2 with the body part 1. The body part 1 and the anode body 6guidable through the basin 2 with the body part 1 are each arranged on aholding arm 8, 9 and longitudinally displaceably guided in a guide 10,11. The guiding direction is perpendicular to the drawing plane. Thusthe body part and the anode body 6 guidable through the basin 2 with thebody part 1 are arranged one after the other seen in movement direction.By way of electric motors 12, 13 the anode body 6 guidable through thebasin 2 with the body part 1 and the body part 1 can be simultaneouslymoved out of the basin 2 and into the basin. Through simultaneousactivation of the electric motor 12, 13 the spacing and the position ofthe anode body 6 guidable through the basin 2 with the body part 1 tothe body part 1 is kept constant. The anode body 6 guidable through thebasin 2 with the body part is elongated in shape and arranged parallelto the longest extension of the body part 1. The guide 10 for the bodypart 1 and the electric motor 12 connected thereto form a transportdevice for guiding the body part 1 through the basin 2.

In a part section through the device from FIG. 1 along the line II-II,FIG. 2 shows that altogether two anode bodies 6, 6′ guidable through thebasin 2 with the body part 1 are arranged on both sides of the body part1. The moveably guided anode bodies 6, 6′ are arranged near a hollowspace 14 of the body part 1. The hollow space 14 of the body part 1shown in the shown exemplary embodiment has an opening 15 facing one ofthe guided anode bodies 6.

While at least one exemplary embodiment has been presented in theforegoing summary and detailed description, it should be appreciatedthat a vast number of variations exist. It should also be appreciatedthat the exemplary embodiment or exemplary embodiments are onlyexamples, and are not intended to limit the scope, applicability, orconfiguration in any way. Rather, the foregoing summary and detaileddescription will provide those skilled in the art with a convenient roadmap for implementing an exemplary embodiment, it being understood thatvarious changes may be made in the function and arrangement of elementsdescribed in an exemplary embodiment without departing from the scope asset forth in the appended claims and their legal equivalents.

1. A device for dip painting of a body part of a motor vehicle,comprising: a basin for receiving a coating liquid; a transport devicefor transporting the body part through the basin; a direct currentsource with an anode body connected to an anode of the direct currentsource; and a guide connected to a cathode of the direct current sourcefor electrically contacting and guiding of the body part through thebasin, wherein the anode body is configured for mounting in asubstantially constant position with respect to the body part in amovement direction of the body part and guidable through the basin withthe body part.
 2. The device for the dip painting according to claim 1,further comprising a further guide connected to the anode of the directcurrent source and the anode body is guided on the further guide.
 3. Thedevice for the dip painting according to claim 1, wherein the guide andthe further guide are arranged substantially parallel to each other andin each case comprise a holding arm configured to hold the anode body.4. The device for the dip painting according to claim 1, wherein theanode body has an elongated shape.
 5. The device for the dip paintingaccording to claim 1, further comprising several anode bodies guidablethrough the basin with the body part are grouped about the body part. 6.The device for the dip painting according to claim 1, further comprisingat least one further fixed anode body in the basin connected to theanode body of the direct voltage source.
 7. The device for the dippainting according to claim 1, wherein the guide and the further guideare arranged substantially parallel to each other and in each casecomprise a holding arm configured to hold the body part.